Non volatile memories, such as for example, flash memories, are associated with appropriate control devices which manage the various possible operations to be performed on the memory itself such as, writing, cancellation, or reading. Possible examples of such control devices are: microprocessors, microcontrollers and DSPs (Digital Signal Processors).
With particular reference to reading operations, the data-transfer speed between the memory in which the data are stored and the control device thereof, is frequently of fundamental importance. The transfer speed, associated with the memory access time, is a parameter which assumes an ever greater importance with increasing memory dimensions.
The known art has proposed different methodologies which seek to increase the transfer speed with respect to that which is observed in the case of random access.
One of these methodologies is the page mode technique which, as is known, provides asynchronous access, i.e. not directly associated with the memory system timing signal. According to this technique, access to the memory for the reading of a word causes the reading of a pre-fixed number of words which constitute a memory page. The first word read is made available following a first pre-fixed time interval (for example, equal to 120 ns), whilst the reading of another word belonging to the same page is completed following a second time interval, shorter than the first, for example, equal to 25 ns. Indeed, this second reading is a selection from within the same page to which there has already been access. If the subsequent word to be read does not belong to the same page, it will be accessed, following the first time interval, on a new page.
Another access technique is that which is denominated as burst mode which, contrary to the former, is a synchronous type, i.e. the timings of the input and output signals are related to a clock signal generated by the system and provided to the memory. Such technology envisages that the access occurs through the transfer of a sequence of words. In order to gain access to the first word it is necessary to wait for M latency cycles in order to allow the memory to execute the reading of N words. The subsequent data appears as output, subsequent to the first word, regulated by the clock signal.
Both page mode technique and the burst mode technique have a drawback associated with the rigidity of the access methodologies. Such rigidity, which is more significant for the second technique, results in the need to use memory control devices which are based on the peculiar characteristics of each of those methods and which in certain cases must envisage the management of additional signals, otherwise not strictly necessary. Furthermore, the known modalities of access do not allow the full exploitation of the possibilities offered by the memories available today.